The present invention relates to the field of hydraulic pumps and motors. More particularly, this invention relates to a multi-piece slipper assembly with a balanced running face. Such slippers have a combination of fatigue strength and mechanical properties which leads to longer life for hydraulic pumps and motors. The invention is useful on axial piston hydrostatic units having slippers with male or female connecting ends.
The fatigue strength of the slippers is a limiting factor in the useful life of hydraulic or hydrostatic pumps and motors. Various materials and combinations of materials have been tried on slippers. However, materials which have adequate fatigue strength do not generally have mechanical properties which are appropriate for the running surface for the slipper. Materials that have good characteristics for a running face generally do not have adequate fatigue strength to provide the desired slipper life.
Bi-metal slippers of different configurations have been tried, but they have high manufacturing costs because they have to be manufactured from pieces of raw material and cannot utilize screw machinery technology. The running face material, usually bronze, is sintered or cast onto steel. Thus, there is a need for a multi-piece slipper assembly which has the desired material characteristics and enables cost-effective, high-volume manufacturing processes to be utilized.
A primary objective of the present invention is the provision of a multi-piece slipper which yields acceptable life and is economical to produce.
A further objective of the present invention is the provision of a two-piece slipper assembly which has a support body of high-strength material and a running face washer attachable and retainable on the support body.
A further objective of the present invention is the provision of a bi-metal running face washer which can be produced by a stamping process.
A further objective of the present invention is the provision of a running face washer which is hydrostatically balanced on the slipper body.
A further objective of the present invention is the provision of a washer which is mechanically self-retaining and will be further retained by normal forces present within the hydrostatic unit during operation.
A further objective of the present invention is the provision of a running face washer which can be replaced at intervals to extend the life of the hydrostatic unit.
A further objective of the present invention is the provision of a slipper and washer combination which is easy to assemble, as well as reliable and durable in use.
These and other objectives will be apparent from the drawings, as well as from the description and claims which follow.